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Author Question: What human activities happening tens or hundreds of kilometers from a coast can still end up ... (Read 27 times)

iveyjurea

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on: Jul 16, 2018
What human activities happening tens or hundreds of kilometers from a coast can still end up affecting the shoreline sediment budget?
 
  What will be an ideal response?

Question 2

Describe how construction of groins and jetties affect adjacent beaches.
 
  What will be an ideal response?


mjbamaung

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Reply #1 on: Jul 16, 2018
Answer to Question 1

Land use in the drainage basin of a stream that delivers sediment to the coast will affect the shoreline sediment budget. Agriculture, mining, timber harvesting, or urbanization typically increase sediment loads to streams so that there are potential gains in the shoreline sediment budget. This effect is counteracted, however, where dams trap sediment in reservoirs and decrease the shoreline sediment budget compared to natural conditions. Increases in sediment budget tend to cause enlargement of beaches whereas decreases cause loss of beaches by wave and current erosion.

Answer to Question 2

Groins are walls built perpendicular to the shoreline to trap sediment being moved by longshore current, which widens the beach on the up-current of the groin. Sediment supply down-current of the groin is reduced, so erosion in this area is accelerated. Jetties function in the same way, but stabilize the location of an inlet. Beaches up-current of a jetty accumulate sediment whereas those down-current of the jetty are sediment-starved and subject to wave and current erosion.


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